The present invention relates to a flat-plate type heat exchanger.
As a conventional type heat exchanger, a heat exchanger is disclosed in the Japanese Patent Gazette JP-A-Sho-36-21644. The Japanese Patent Gazette JP-A-Sho-36-21644 discloses a heat transfer unit, wherein projections are formed in a predetermined distribution on a flat plate, the flat plate is folded back in multiple layers alternately with a predetermined width, a gap for the projection is formed between the flat plates, and boundaries of heat transfer unit are formed by the flat plate. And the Japanese Patent Gazette JP-A-Sho-36-21644 also discloses a heat exchanger wherein a high temperature fluid and a low temperature fluid are passed through the gaps, and heat exchange operation is performed via the heat transfer unit.
The conventional type heat exchanger has advantages in that it is simple in construction and lower in the manufacturing cost and has high thermal efficiency. On the other hand, the heat transfer unit is accommodated in a casing, and the casing and the heat transfer unit are welded together to ensure air-tightness and liquid-tightness. In this respect, the casing and the heat transfer unit cannot be disassembled, and it has been difficult to perform maintenance operation such as cleaning of the heat transfer unit.